Method of manufacturing silicon carbide, silicon carbide, composite material, and semiconductor element

ABSTRACT

To provide a method of manufacturing silicon carbide by forming silicon carbide on a substrate surface from an atmosphere containing a silicon carbide feedstock gas comprising at least a silicon source gas and a carbon source gas under condition 1 or 2 below:  
     Condition 1: the partial pressure ps of silicon source gas is constant (with ps&gt;0), the partial pressure of carbon source gas consists of a state pc 1  and a state pc 2  that are repeated in alternating fashion, wherein pc 1  and pc 2  denote partial pressures of carbon source gas, pc 1&gt; pc 2 , and pc 1 /ps falls within a range of 1-10 times the attachment coefficient ratio (Ss/Sc), pc 2 /ps falls within a range of less than one time Ss/Sc;  
     Condition 2: the partial pressure pc of carbon source gas is constant (with pc&gt;0), the partial pressure of silicon source gas consists of a state ps 1  and a state ps 2  that are repeated in alternating fashion, wherein ps 1  and ps 2  denote partial pressures of silicon source gas, ps 1&lt; ps 2 , and pc/ps 1  falls within a range of 1-10 times Ss/Sc, pc/ps 2  falls within a range of less than one time Ss/Sc.

BACKGROUND OF THE INVENTION

[0001] 1. Field of the Invention

[0002] The present invention relates to methods of manufacturing siliconcarbide (for example, thin films and ingots) employed as a substratematerial in semiconductor devices and X-ray masks, chiefly siliconcarbide employed in the components of semiconductor manufacturingdevices, dummy wafers employed in semiconductor element manufacturingsteps, and silicon carbide structural members (for example, heaters,anticorrosion products (screws, bearings), and the like).

[0003] 2. Related Art

[0004] Silicon carbide is a semiconductor with a broad forbiddenbandwidth of 2.2 eV or greater and is a thermally, chemically, andmechanically stable crystal. Further, due to high thermal conductivity,its application as a semiconductor material under conditions of highfrequency, high power, high temperature, and the like is anticipated.

[0005] Methods of manufacturing silicon carbide include reacting cokeand silicon on a heated carbon surface and precipitating silicon carbideon a carbon surface (the Atchison method); heating and sublimatingsilicon carbide formed by the Atchison method and recrystallizing it(sublimation method, improved Reilly method); the liquid depositionmethod in which silicon is melted in a carbon crucible and the suspendedcarbon and silicon are reacted in the crucible while drawing the productupward; and the like.

[0006] Methods employed to obtain high purity silicon carbide films withfew planar defects include chemical vapor deposition (CVD) in which acarbon source gas and a silicon source gas are thermally reacted atordinary pressure or under a reduced pressure atmosphere andprecipitated onto a substrate surface; and atomic layer epitaxy (ALE) inwhich a silicon source and a carbon source are alternately adsorbed ontoa substrate surface, and epitaxially growing silicon carbide whileextending the crystalline properties of the substrate.

[0007] Although the Atchison method produces inexpensive, largequantities of silicon carbide, the precipitating silicon carbide isamorphous, comprising crystalline polymorphism and large quantities ofimpurities. In particular, this method cannot be employed to manufacturesemiconductor materials in which defects and impurities are problematic.

[0008] The improved Reilly method reduces the problems of crystallinepolymorphism, amorphism, and the like associated with the Atchisonmethod. However, it is difficult to reduce the impurities incorporatedinto the crystal, and increasing the area of the crystal and decreasingthe number of defects are no simple tasks.

[0009] The method that is generally employed to reduce the crystaldefects and impurities that are problematic in the improved Reillymethod is to use CVD or ALE to epitaxially grow silicon carbide whilereducing the defect density and impurities on a silicon carbidesubstrate obtained by the improved Reilly method. However, since thearea of the crystals obtained by these methods is limited to the area ofthe silicon carbide obtained by the improved Reilly method, large-area,high-quality silicon carbide cannot be obtained.

[0010] To increase the area of silicon carbide, the general method hasbeen devised of using CVD or ALE to heteroepitaxially grow a siliconcarbide layer on a single crystal silicon substrate employed as asemiconductor material. However, high concentrations of defects areproduced at the interface of the silicon substrate and the siliconcarbide. Thus, the quality of the crystal is poorer than that ofepitaxially grown silicon carbide layers formed on silicon carbidesubstrates obtained by the improved Reilly method. When employingheteroepitaxial growth, crystal quality can be improved by increasingthe thickness of the film of silicon carbide being grown. However, sincethe rate of silicon carbide growth by CVD or ALE is extremely low, theapplication of silicon carbide obtained by heteroepitaxial growth iscurrently impeded.

[0011] The rate of growth of silicon carbide can be increased to someextent by increasing the partial pressure of the starting gasses usingCVD. However, the faster the growth rate, the more crystal defects tendto increase in the silicon carbide. Since the ALE method requires that acertain quantity of atoms or molecules be uniformly adsorbed to thesubstrate surface under thermal equilibrium, increasing the growth rateof silicon carbide by increasing the amount of gas being fed as is donein CVD is undesirable.

[0012] Accordingly, the object of the present invention is to provide amethod of manufacturing silicon carbide affording adequate ease ofproduction by increasing the growth rate of silicon carbide in gas vaporgrowth without increasing crystal defects.

[0013] That is, for example, a further object of the present inventionis to provide a method of manufacturing silicon carbide of a qualitysuitable for use as a semiconductor element material with fewer crystaldefects and affording adequate ease of production even inheteroepitaxial growth employing a substrate other than silicon carbide.A further object of the manufacturing method of the present invention isto obtain silicon carbide not just as a thin film, but also as an ingotor structural member.

[0014] A still further object of the present invention is to providesilicon carbide (not just thin films, but also ingots and structuralmembers) having heretofore unseen dimensions (bores) in the form ofsilicon carbide of a quality suitable for use as a semiconductor elementmaterial with reduced crystal defects.

[0015] Yet another object of the present invention is to provide asemiconductor element employing the above-described silicon carbide as asubstrate, and to provide a method of manufacturing composite materialsemploying the above-described silicon carbide as seed crystal.

SUMMARY OF THE INVENTION

[0016] The aforementioned objects can be achieved by the presentinvention as follows.

[0017] In accordance with the present invention, there is provided amethod of manufacturing silicon carbide by forming silicon carbide froman atmosphere containing a silicon carbide feedstock gas on a substratesurface, characterized in that:

[0018] said silicon carbide feedstock gas comprises at least a siliconsource gas and a carbon source gas;

[0019] the partial pressure ps of said silicon source gas in saidatmosphere is constant (with ps>0), the partial pressure of said carbonsource gas in said atmosphere consists of a state pc1 and a state pc2

[0020] (where pc1 and pc2 denote partial pressures of said carbon sourcegas, pc1>pc2, and the partial pressure ratio (pc1/ps) falls within arange of 1-10 times the attachment coefficient ratio (Ss/Sc), thepartial pressure ratio (pc2/ps) falls within a range of less than onetime the attachment coefficient ratio (Ss/Sc)

[0021] (where Ss denotes the attachment coefficient of silicon sourcegas to the silicon carbide substrate at the substrate temperature duringformation of said silicon carbide, and Sc denotes the attachmentcoefficient of carbon source gas to the silicon carbide substrate at thesubstrate temperature during the forming of said silicon carbide))

[0022] that are repeated in alternating fashion (referred to ascondition 1 below); or

[0023] the partial pressure pc of said carbon source gas in saidatmosphere is constant (with pc>0), the partial pressure of said siliconsource gas in said atmosphere consists of a state ps1 and a state ps2

[0024] (where ps1 and ps2 denote partial pressures of said siliconsource gas, ps1<ps2, and the partial pressure ratio (pc/ps1) fallswithin a range of 1-10 times the attachment coefficient ratio (Ss/Sc),the partial pressure ratio (pc/ps2) falls within a range of less thanone time the attachment coefficient ratio (Ss/Sc)

[0025] (where Ss denotes the attachment coefficient of silicon sourcegas to the silicon carbide substrate at the substrate temperature duringformation of said silicon carbide, and Sc denotes the attachmentcoefficient of carbon source gas to the silicon carbide substrate at thesubstrate temperature during the forming of said silicon carbide))

[0026] that are repeated in alternating fashion (referred to ascondition 2 below).

[0027] In the above manufacturing method of silicon carbide, thefollowings are preferred.

[0028] In condition 1, pc1 and pc2 each continue for a prescribedperiod, and in condition 2, ps1 and ps2 each continue for a prescribedperiod.

[0029] Silicon carbide is formed on a substrate the temperature of whichis not less than 900° C.

[0030] The above silicon source gas is at least one member selected fromthe group consisting of SiH₄, Si₂H₆, SiCl₄, SiHCl₃, SiH₂Cl₂, Si(CH₃)₄,SiH₂(CH₃)₂, SiH(CH₃)_(3, and Si) ₂(CH₃)₆, and said carbon source gas isat least one member selected from the group consisting of CH₄, C₃H₈,C₂H₅, C₂H₆, C₂H₂, C₂H₄, CCl₄, CHF₃, CF₄.

[0031] Pc2 or ps1 is essentially 0.

[0032] Pc2 is essentially 0, the time during which the partial pressureof the carbon source gas is set to pc1 is 0.1-30 seconds, and the timeduring which the partial pressure of the carbon source gas is set to pc2is 0.1-30 seconds.

[0033] The present invention further relates to a method ofmanufacturing silicon carbide characterized in that the silicon carbidemanufactured in any of claims 1-6 is employed as seed crystal and inthat silicon carbide is formed on said seed crystal by vapor phaseepitaxy, sublimation recrystallization, or liquid deposition.

[0034] In the above manufacturing method of silicon carbide, thepreferred is that silicon carbide blocks 4-6 inches in bore are formedby vapor phase epitaxy, sublimation recrystallization, or liquiddeposition.

[0035] The present invention further relates to a silicon carbide blockcharacterized by having a bore of 4-6 inches.

[0036] In the above silicon carbide block, the preferred is that theplanar defect density is not more than 10³/cm².

[0037] The present invention further relates to a semiconductor elementemploying as substrate the silicon carbide block described above.

[0038] The present invention further relates to a method ofmanufacturing composite materials characterized in that silicon carbidemanufactured by the above-mentioned method is employed as seed crystaland diamond and/or gallium nitride is formed on said seed crystal.

BRIEF DESCRIPTION OF THE DRAWINGS

[0039]FIG. 1 is an example of the cycle of condition 1 of the presentinvention.

[0040]FIG. 2 is an example of the cycle of condition 2 of the presentinvention.

[0041]FIG. 3 is a type drawing descriptive of the operation of thepresent invention: (1) shows how the silicon source is fed onto thesubstrate, (2) shows how the silicon source fed onto the substrate formsan epitaxial growth layer of silicon, (3) shows how the epitaxial growthlayer of silicon formed on the substrate reacts with the carbon sourceto form silicon carbide, and (4) shows how the carbon source forms anadsorption layer on the silicon carbide layer, impeding adsorption ofthe silicon source.

[0042]FIG. 4 is the method of supplying feedstock gas in ComparativeExample 1.

[0043]FIG. 5 is the method of supplying feedstock gas in Embodiment 1.

[0044]FIG. 6 is the method of supplying feedstock gas in Embodiment 2.

[0045]FIG. 7 is the method of supplying feedstock gas in Embodiment 3.

[0046]FIG. 8 is the method of supplying feedstock gas in Embodiment 4.

[0047]FIG. 9 is the method of supplying feedstock gas in Embodiment 5.

[0048]FIG. 10 is a schematic drawing of the method used to measure theattachment coefficient ratio.

[0049]FIG. 11 is a graph showing the change over time of the quantity ofgas that is fed.

[0050]FIG. 12 is a graph showing the change over time of the number n(t)(relative value) of gas molecules desorbing from the substrate surfaceas measured by quadrupole mass spectrometry.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0051] The method of manufacturing silicon carbide of the presentinvention is chiefly a method of manufacturing thin films of siliconcarbide on a substrate surface from an atmosphere containing siliconcarbide feedstock gases. However, it is not limited to thin films ofsilicon carbide, and can be used to manufacture silicon carbide ingotsand structural members of silicon carbide.

[0052] The method of manufacturing silicon carbide of the presentinvention is characterized by conditions 1 and 2 below.

[0053] Condition 1: The silicon carbide feedstock gas comprises at leasta silicon source gas and a carbon source gas. The partial pressure ps ofthe silicon source gas in the atmosphere is constant (with ps>0), andthe partial pressure of the carbon source gas repeatedly alternatesbetween a state pc1 and a state pc2.

[0054] Condition 2: The silicon carbide feedstock gas comprises at leasta silicon source gas and a carbon source gas. The partial pressure pc ofthe carbon source gas is constant (with pc>0), and the partial pressureof the silicon source gas repeatedly alternates between a state ps1 anda state ps2.

[0055]FIG. 1 shows an example of the cycle of condition 1.

[0056] In condition 1, the partial pressure ps of the silicon source gasis constant in the atmosphere. However, ps>0. The partial pressure ofthe carbon source gas in the atmosphere repeatedly alternates between astate pc1 and a state pc2. That is, since pc1>pc2, the partial pressureof the carbon source gas is increased. Although pc1>pc2, pc2 canessentially be 0. What is meant in the present Specification by thepartial pressure being essentially 0 is not greater than 10⁻⁵ Torr. Thetime (tc1) during which the pressure of the carbon source gas is madepc1 and the time (tc2) during which the partial pressure of the carbonsource gas is made pc2 are repeatedly alternated.

[0057] In condition 1, during time tc2 when the partial pressure of thecarbon source gas is made pc2, the partial pressure of the carbon sourcegas is lower than the silicon source gas, and so long as pc2 is notzero, silicon carbide precipitates. However, Si also precipitates inthis state. Subsequently, during time tc1 when the partial pressure ofthe carbon source gas is pc1, the partial pressure of the carbon sourcegas becomes relatively high, and simultaneously with the precipitationof silicon carbide, Si reacts with C supplied by the silicon source gas,creating silicon carbide. To permit the creation of such states, tc1 andtc2, ps, pc1 and pc2, the type of silicon source gas and carbon sourcegas, the substrate temperature, the capacity of the reaction vessel, andthe like are considered and suitably determined. For example, tc1 can beset to within a range of 0.1-60 sec and tc2 to within a range of 0.1-90sec. Setting pc2 to 0; setting time tc1, when the partial pressure ofthe carbon gas is set to pc1, to 0.1-30 sec; and setting time tc2, whenthe partial pressure of the carbon source gas is set to pc2, to 0.1-30sec is particularly desirable from the viewpoint of decreasing crystaldefects in the silicon carbide and increasing the growth rate.

[0058] Further, in condition 1, the partial pressure ratio (pc1/ps) isset to within a range of 1-10 times the attachment coefficient ratio(Ss/Sc) and the partial gas ratio (pc2/ps) is set to within a range ofless than one time the attachment coefficient ratio (Ss/Sc). Thus,during time tc2 when the partial pressure of the carbon source gas ispc2, silicon carbide and Si precipitate simultaneously, andsubsequently, during time tc1 when the partial pressure of the carbonsource gas is pc1, the precipitation of silicon carbide and theformation of silicon carbide through the reaction of precipitated Si andC occur simultaneously. The attachment coefficient ratio (Ss/Sc) can becalculated by a method described further below.

[0059] An example of the cycle of condition 2 is shown in FIG. 2.

[0060] In condition 2, the partial pressure pc of the carbon source gasin the atmosphere is held constant. However, pc>0. The state where thepartial pressure of the silicon source gas in the atmosphere is ps1 andthe state in which it is ps2 are repeatedly alternated. That is, sinceps1<ps2, the partial pressure of the silicon source gas is increased.Although ps1<ps2, ps1 can be essentially 0. The time (ts1) during whichthe partial pressure of the silicon source gas is made ps1 and the time(ts2) during which the partial pressure of the silicon gas source ismade ps2 are repeatedly alternated.

[0061] In condition 2, during time ts2 when the partial pressure of thesilicon source gas is made ps2, the partial pressure of the carbonsource gas is lower than that of the silicon source gas and siliconcarbide precipitates, but Si also precipitates during that state.Subsequently, during time ts1 when the partial pressure of the siliconsource gas is made ps1, the partial pressure of the silicon source gasbecomes relatively low, and Si reacts with C supplied by the carbonsource gas to form silicon carbide simultaneously with the precipitationof silicon carbide. To permit the creation of such states, ts1 and ts2,pc, psi and ps2, the type of silicon source gas and carbon source gas,the substrate temperature, the capacity of the reaction vessel, and thelike are considered and suitably determined. For example, ts1 can be setto within a range of 0.1-60 sec and ts2 to within a range of 0.1-60 sec.

[0062] Further, in condition 2, partial pressure ratio (pc/ps1) is setto within a range of 1-10 times the attachment coefficient ratio(Ss/Sc), and partial pressure ratio (pc/ps2) is set to within a range ofless than one time attachment coefficient ratio (Ss/Sc). Thus, duringtime ts2 when the partial pressure of the silicon source gas is ps2,precipitation of silicon carbide and Si occurs simultaneously, andsubsequently, during time ts1 when the partial pressure of the siliconsource gas is ps1, precipitation of silicon carbide and the formation ofsilicon carbide through the reaction of precipitated Si and C occursimultaneously.

[0063] Attachment coefficient ratio (Ss/Sc) can be determined in thefollowing manner.

[0064] A valve is used to blow a pulse of either the carbon source gasor the silicon source gas onto the surface of the silicon carbidesubstrate. The temperature of the silicon carbide substrate is preset tothe substrate temperature for forming silicon carbide.

[0065] The partial pressure at T=0 is instantaneously raised to a fixedlevel.

[0066] Gas molecules temporarily attached to the surface of thesubstrate are desorbed, but the quantity (a relative value) of the gasmolecules that are desorbed is monitored with a quadrupole massspectrometer. A collimator is positioned between the substrate and thequadrupole mass spectrometer so that in this process, just the gasmolecules that are desorbed from the substrate enter the massspectrometer. (FIG. 10 is a schematic of the measurement system.)

[0067] The graph of FIG. 11 shows the change over time of the level ofgas supply. The graph of FIG. 12 shows the change over time in thequantity n(t) (relative value) of gas molecules desorbed from thesurface of the substrate being measured by the quadrupole massspectrometer.

[0068] Let τ denote the time coordinates of the point of intersection ofthe tangent of n(t) when t=0 and the asymptotic line when τ→∞. Let τc(the average residence time of the carbon source gas on the surface ofthe substrate) denote τ when the gas employed is the carbon source gas.Let τs (the average residence time of the silicon source gas on thesurface of the substrate) denote τ when the gas employed is the siliconsource gas. The attachment coefficient ratio can then be calculated fromthe relation Sc/Ss=τc/τs.

[0069] During the formation of silicon carbide by the manufacturingmethod of the present invention, setting the substrate temperature tonot less than 900° C. promotes the decomposition of molecules adheringto the substrate surface and promotes the reaction, and is suitable fromthe viewpoint of making it possible to establish a prescribed relation(the relation specified by condition 1 and condition 2) between thepartial pressure ratio and the attachment coefficient ratio that isindependent of the types of gas. The substrate temperature desirablefalls with a range of 1,100-1,370° C.

[0070] Examples of substrates suitable for use in forming siliconcarbide are Si, SiC, TiC, sapphire, and diamond.

[0071] The operation of the manufacturing method of the presentinvention will be described based on FIG. 3. FIG. 3 describes the caseof condition 1.

[0072] As shown by FIG. 3 (1), when a silicon source is continuously fedto the substrate surface (ps=constant, pc2=0), the silicon sourcethermally decomposes, for example, on the surface of the substrate thathas been heated to not less than 900° C. and a single crystal of siliconforms on the substrate surface (FIG. 3(2)). Here, when the carbon sourceis temporarily supplied (at pc2), the formation of the silicon layer onthe substrate surface is inhibited and the silicon layer that formed onthe substrate surface prior to the introduction of the carbon sourcesimultaneously reacts with the carbon source, forming silicon carbide(FIG. 3(3)). In this process, when the partial pressure of the carbonsource has been set to pc2, the attachment coefficient of the carbonsource to Sc, the partial pressure of the silicon source to ps, and theattachment coefficient of the silicon source to Ss, and when pc2 or psis controlled to maintain a relation where pc2/ps during the carbonsource supply is not less than one time and not more than ten timesSs/Sc, the incorporation of the silicon source onto the substratesurface is inhibited during feeding of the carbon source (FIG. 3(4)).

[0073] When the carbon source is fed intermittently as set forth above,the process of silicon layer epitaxial growth on the substrate surfaceand process of the formation of silicon carbide through the reaction ofthe silicon layer that has been epitaxially grown and the carbon sourceare completely separated in time, yielding single-crystal siliconcarbide with few defects. Further, since the carbon source adsorptionlayer is segregated in the vicinity of the substrate surface duringfeeding of the carbon source in the present invention and the siliconsource remains, as soon as feeding of the carbon source is stopped, thesilicon layer grows epitaxially and the growth rate of the siliconcarbide increases. However, when pc2/ps falls below Ss/Sc, the siliconsource is incorporated into the substrate surface even during feeding ofthe carbon source, yielding silicon carbide in which there is a shift incrystal orientation with the underlayer, or microcrystals of silicon arepicked up in the silicon carbide, precluding the effect of the presentinvention. To achieve adequate mass production (growth rate of siliconcarbide) based on the present invention, the time during which thecarbon source is fed per cycle is preferably not more than 30 sec.However, at less than 0.1 sec, it is difficult to supply an adequatecarbon source. The interval of the intermittent supply of carbon sourceis desirably not less than 0.1 sec to desorb the carbon source that hasadsorbed onto the substrate surface and to promote the growth of siliconon the substrate surface. However, at greater than 30 sec, the growthrate of the silicon carbide tends to be compromised.

[0074] Mechanism of deposition of silicon carbide and the like incondition 1 has been described above; that of condition 2 issubstantially identical therewith.

[0075] Although the silicon source gas and the carbon source gasemployed in the manufacturing method of the present method are notspecifically limited, at least one member from among the groupconsisting of SiH₄, Si₂H₆, SiCl₄, SiHCl₃, SiH₂Cl₂, Si(CH₃)₄, SiH₂(CH₃)₂,SiH(CH₃)₃, and Si₂(CH₃)₆ can be employed as the silicon source gas, forexample. Further, at least one member from among the group consisting ofCH₄, C₃H₈, C₂H₅, C₂H₆, C₂H₂, C₂H₄, CCl₄, CHF₃, and CF₄ carbon sourcegas, for example.

[0076] Based on the method of manufacturing silicon carbide of thepresent invention as set forth above, large-bore silicon carbide withfew (or no) crystal defects can be manufactured with good ease ofproduction. In particular, even when the substrate is something otherthan silicon carbide—single crystal silicon, for example—it is possibleto manufacture large-bore silicon carbide with few (or no) crystaldefects with good ease of production.

[0077] The present invention covers methods of manufacturing siliconcarbide characterized in that silicon carbide manufactured by theabove-described manufacturing method of the present invention,particularly thin film silicon carbide, is employed as seed crystal, andsilicon carbide is formed on this seed crystal by vapor phase epitaxy,sublimation recrystallization, or liquid deposition.

[0078] Vapor phase epitaxy, sublimation recrystallization, and liquiddeposition methods for forming silicon carbide are as follows.

[0079] In vapor phase epitaxy methods of forming silicon carbide, atleast two types of gas consisting of a carbon source and a siliconsource, or at least one type of gas comprising both carbon and silicon,is thermally decomposed in a vapor phase or on the surface of thesubstrate and reacted, yielding silicon carbide on the substratesurface. For example, an SiC substrate based on the present invention isemployed as seed crystal, and while being heated under vacuum to 1,200°C., 1 sccm of silane gas and 0.5 sccm of propane gas are introduced, and1 slm of a noble gas in the form of Ar is fed. While maintaining thepressure of the reaction system at 100 mTorr, SiC is grown again on theseed crystal SiC substrate.

[0080] In sublimation recrystallization methods of forming siliconcarbide, silicon carbide feedstock is charged to a graphite crucible, aseed crystal of the silicon carbide of the present invention isintroduced opposite the feedstock, and while controlling the temperatureof the feedstock to be somewhat higher than that of the seed crystal,the crucible is heated to not less than 2,000° C. at one atmosphericpressure, causing the feedstock to sublimate and recrystallize on theseed crystal.

[0081] In liquid deposition methods of forming silicon carbide, Si ismelted in a carbon crucible heated to 1,500° C., the surface of thesilicon carbide (seed crystal) of the present invention is contactedwith the liquid surface, and silicon carbide grows on the seed crystalfrom molten Si and suspended carbon in the molten Si.

[0082] Silicon carbide blocks (for example, ingots and structuralmembers) with bores of from 4-6 inches (ranging from 100-160 mm) can beformed by the above-described manufacturing methods (vapor phaseepitaxy, sublimation recrystallization, and liquid deposition). Here,the term “bore” corresponds to the diameter of the substrate employed inthe above-described manufacturing methods. In conventional siliconcarbide blocks, the bore runs up to about three inches, but based on themanufacturing method of the present invention, silicon carbide blockswith bores of 4-6 inches (equivalent to 102-152 mm, ranging from 100-160mm) can be obtained. Further, the blocks obtained have planar defectdensities of not more than 10³/cm².

[0083] Accordingly, the present invention covers silicon carbide blockscharacterized by bores of from 4-6 inches. These silicon carbide blocksalso have planar defect densities of not more than 10³/cm².

[0084] The present invention further covers semiconductor elementsemploying the above-described silicon carbide blocks of the presentinvention as substrates. Examples of such semiconductor elements areSchottky diodes, blue light-emitting diodes, and other power devices andlight-emitting elements.

[0085] Further, these semiconductor elements can also be manufactured bymethods of manufacturing composite materials including the formation ofdiamond and/or gallium nitride on seed crystals of silicon carbidemanufactured by the above-described manufacturing method of the presentinvention, for example.

[0086] Diamond can be formed on the seed crystal in the followingmanner.

[0087] A seed crystal is placed in a vacuum chamber and heated to 500°C., after which propane gas is introduced into the vacuum chamber. Thepressure within the chamber is then regulated to 10 mTorr with anevacuation system. Next, a high frequency of 13.56 MHz (200 W) isapplied between the seed crystal and a flat electrode facing the seedcrystal and a plasma is formed. The carbon decomposed by the plasma isdeposited on the seed crystal and remains at the correct crystalposition to form diamond on the seed crystal.

[0088] Further, the formation of gallium nitride on seed crystal can beperformed as follows.

[0089] A silicon carbide (seed crystal) substrate obtained by themanufacturing method of the present invention is placed in a vacuumvessel and heated to 1040° C. Next, 10 slm of ammonia and 0.5 sccm oftrimethylgallium are introduced into the reaction vessel, and while thevarious gases decompose on the seed crystal, a GaN forming reactiontakes place at correct crystal position.

[0090] The present disclosure relates to the subject matter contained inJapanese Patent Application No. 2000-162048 filed on May 31, 2000, whichis expressly incorporated herein by reference in its entirety.

[0091] [Embodiments]

[0092] Embodiments of the present invention are described below.

[0093] In the embodiments and comparative examples, the partialpressures of the silicon source gas and carbon source gas areproportional to the feed flow rates. Thus, the partial pressure ratio isequal to the flow rate ratio. Comparative Example 1

[0094] (Intermittent Feeding of Both Silicon Source and Carbon Source)

[0095] Employing the {001} plane of a single-crystal silicon substrateas the single-crystal growth substrate, the substrate was heated to atemperature of 1,200° C., and cubic silicon carbide was epitaxiallygrown on the upper layer thereof. Using a cold wall type CVD device, thepressure was adjusted through the introduction of Ar to a pressure of100 mTorr during growth. The growth of silicon carbide on the siliconsubstrate was conducted by feeding feedstock gases in the form ofSiH₂Cl₂ and C₂H₂. The ratio Ss/Sc of the attachment coefficients ofSiH₂Cl₂ and C₂H₂ on the surface of the silicon carbide was 0.25.

[0096] A comparative example will be given next based on FIG. 4. Siliconcarbide was grown by feeding SiH₂Cl₂ and C₂H₂ at separate times. SiH₂Cl₂feeding was conducted continuously for 5 sec at a partial pressure of 10sccm. Next, after stopping the feeding of gases other than Ar, C₂H₂ wasfed for 5 sec.

[0097] After feeding C₂H₂ for 5 sec, the feeding of gases other than Arwas stopped, and SiH₂Cl₂ feeding was begun. This alternating feeding ofgases was repeated 1,000 times, yielding a cubic silicon carbide film onthe silicon substrate. Growing the silicon carbide took 5.56 hr. As aresult of the growth, a 0.8 μm single crystal of silicon carbide wasobtained on the silicon substrate. As a result, the growth rate of thesilicon carbide was 0.144 μm/hr. However, surface defects such as antiphase boundaries and twin crystal bands were present on the surface ofthe silicon carbide at a density of 10³/cm².

[0098] Embodiment 1 (Continuous Feeding of Silicon Source, IntermittentFeeding of Carbon Source)

[0099] Employing the {001} plane of a single-crystal silicon substrateas the single-crystal growth substrate, the substrate was heated to atemperature of 1,200° C., and 3C-silicon carbide was epitaxially grownon the upper layer thereof. Using a cold wall type CVD device, thepressure was adjusted through the introduction of Ar to a pressure of100 mTorr during growth. The growth of silicon carbide on the siliconsubstrate was conducted by feeding feedstock gases in the form ofSiH₂Cl₂ and C₂H₂. The ratio Ss/Sc of the attachment coefficients ofSiH₂Cl₂ and C₂H₂ on the surface of the silicon carbide was 0.25.

[0100] The embodiment of the present invention will be described basedon FIG. 5. While continuously feeding SiH₂Cl₂ at a partial pressure of10 sccm, C₂H₂ was intermittently fed to grow silicon carbide. Thepartial pressure of the SiH₂Cl₂ was 10 sccm. C₂H₂ was intermittently fed1,000 times at intervals of 5 sec at a partial pressure of 10 sccm. Eachtime, the C₂H₂ was fed for 5 sec. Growth of silicon carbide required 2.8hr. As a result of the growth, 67 μm of single crystal silicon carbidewas obtained on the silicon substrate. The effective growth rate ofsilicon carbide was 24 μm/hr. Further, surface defects such as antiphase boundaries and twin crystal bands had been eliminated from thesurface of the crystal obtained. In this manner, the use of the presentinvention permitted an accelerated rate of silicon carbide growthexceeding 10 μm/hr and permitted a substantial decrease in crystaldefects. (fc2/fs=4×Ss/Sc, fc1=0, that is pc2/ps=4×Ss/Sc, pcl=0).

[0101] Although a cold wall CVD device was employed in the presentembodiment, a hot wall type CVD device may also be employed to achieveresults identical to those of the present embodiment.

[0102] Further, although the silicon {001} plane was employed assubstrate, the same rapid growth and crystal properties as in thepresent embodiment can be achieved using the silicon {111} plane, cubicsilicon carbide {001} plane, cubic silicon carbide {111} plane, cubicsilicon carbide {−1, −1, −1} plane, hexagonal silicon carbide {1, 1, −2,0} plane, hexagonal silicon carbide {0, 0, 0, 1} plane, hexagonalsilicon carbide {0,0,0,−1} plane, and hexagonal silicon carbide {1, −10,0} plane.

[0103] Although C₂H₂ was employed as the carbon source and SiH₂Cl₂ asthe silicon source in the present embodiment, so long as the partialpressure ratio (flow rate ratio) of the carbon source to the siliconsource is not less than one time and not more than ten times theattachment coefficient ratio, at least one member selected from thegroup consisting of CH₄, C₃H₈, C₂H₅, C₂H₆, C₂H₄, C₂H₆, CCl₄, CHF₃, andCF₄ can be employed as the carbon source, and at least one memberselected from the group consisting of SiH₄, Si₂H₆, SiCl₄, SiHCl₃,Si(CH₃)₄, SiH₂(CH₃)₂, SiH(CH₃)₃, and Si₂(CH₃)₆ can be employed as thecarbon source to achieve the effect of the present invention.

[0104] Embodiment 2 (Continuous Supply of Silicon, Intermittent Supplyof Carbon)

[0105] Employing the {001} plane of a single-crystal silicon substrateas the single-crystal growth substrate, the substrate was heated to atemperature of 1,200° C., and 3C-silicon carbide was epitaxially grownon the upper layer thereof. Using a cold wall type CVD device, thepressure was adjusted through the introduction of Ar to a pressure of100 mTorr during growth. The growth of silicon carbide on the siliconsubstrate was conducted by feeding feedstock gases in the form ofSiH₂Cl₂ and C₂H₂. The ratio Ss/Sc of the attachment coefficients ofSiH₂Cl₂ and C₂H₂ on the surface of the silicon carbide was 0.25.

[0106] The embodiment of the present invention will be described basedon FIG. 6 below. While continuously feeding SiH₂Cl₂ at a flow rate of 10sccm, C₂H₂ was intermittently fed to grow silicon carbide. The SiH₂Cl₂flow rate was a constant 10 sccm. C₂H₂ was intermittently fed 1,000times at intervals of 5 sec. Each time, C₂H₂ was fed for 5 sec. However,the flow rate fc of C₂H₂ was treated as a parameter and fc2 was variedfrom 0.5-200 sccm and the change in silicon carbide growth rate wasobserved. (fc2/fs=4×Ss/Sc, fc1=0, that is pc2/ps=4×Ss/Sc, pc1=0).

[0107] Table 1 shows the changes in growth rates of silicon carbide byfc2. When fc2/fs (that is, pc2/ps) was Ss/Sc (0.25) or greater, thegrowth rate of silicon carbide exceeded 10 μm/hr and the effect of thepresent invention was apparent. However, when fc2/fs (that is, pc2/ps)was less than Ss/Sc (0.25), not only did the growth rate of siliconcarbide decrease, but silicon precipitated in the silicon carbide,precluding the effect of the present invention. Further, when fc2/fs(that is, pc2/ps) exceeded 2.5, the level of adsorption of C₂H₂ on thesubstrate surface increased. Since adsorption of SiH₂Cl₂ was blocked,the growth rate of silicon carbide dropped precipitously, precluding theeffect of the present invention. Silicon carbide grown at an fc2/fs ofnot less than 0.15 and not greater than 3.5 did not exhibit surfacedefects such as anti phase boundaries and twin crystals.

[0108] As set forth above, the use of the method of manufacturingsilicon carbide provided by the present invention yields a siliconcarbide growth rate of 10 μm/hr or greater and improves quality. TABLE 1silicon carbide growth rate fc2 (sccm) fc2/fs (pc2/ps) (μm/hr) 0.5 0.05silicon precipitation 1 0.1 silicon precipitation 1.5 0.15 5 1.7 0.17 52 0.2 7 2.3 0.23 8 2.5 0.25 11 3 0.3 21 4 0.4 23 5 0.5 24 10 1 24 15 1.518 20 2 13 25 2.5 13 30 3 5 35 3.5 3 40 4 0.5 50 5 0 100 10 0 200 20 0

[0109] Although a cold wall type CVD device was employed in the presentembodiment, the same effects can be achieved in the present embodimentusing a hot wall type CVD advice.

[0110] Further, although the silicon {001} plane was employed assubstrate, the same rapid growth and crystal properties as in thepresent embodiment can be achieved using the silicon {111} plane, cubicsilicon carbide {001} plane, cubic silicon carbide {111} plane, cubicsilicon carbide {−1, −1, −1} plane, hexagonal silicon carbide {1,1,−2,0}plane, hexagonal silicon carbide {0, 0, 0, 1} plane, hexagonal siliconcarbide {0, 0, 0,−1} plane, and hexagonal silicon carbide {1, −10, 0}plane.

[0111] Although C₂H₂ was employed as the carbon source and SiH₂Cl₂ asthe silicon source in the present embodiment, so long as the partialpressure ratio (flow rate ratio) of the carbon source to the siliconsource is not less than one time and not more than ten times theattachment coefficient ratio, at least one member selected from thegroup consisting of CH₄, C₃H₈, C₂H₅, C₂H₆, C₂H₄, C₂H₆, CCl₄, CHF₃, andCF₄can be employed as the carbon source, and at least one memberselected from the group consisting of SiH₄, Si₂H₆, SiCl₄, SiHCl₃,Si(CH₃)₄, SiH₂(CH₃)₂, SiH(CH₃)₃, and Si₂(CH₃)₆ can be employed as thecarbon source to achieve the effect of the present invention.

[0112] Embodiment 3

[0113] Employing the {001} plane of a single-crystal silicon substrateas the single-crystal growth substrate, the substrate was heated to atemperature of 1,300° C., and cubic silicon carbide was epitaxiallygrown on the upper layer thereof. Using a cold wall type CVD device, thepressure was adjusted through the introduction of H₂ to a pressure of 60mTorr during growth. The growth of silicon carbide on the siliconsubstrate was conducted by feeding feedstock gases in the form of SiCl₄and C₂H₅. The ratio Ss/Sc of the attachment coefficients of SiCl₄ andC₂H₅ on the surface of the silicon carbide was 0.68.

[0114] The embodiment of the present invention will be described basedon FIG. 7 below. While continuously feeding SiCl₄ at a flow rate of 20sccm, C₂H₅ was intermittently fed to grow silicon carbide. C₂H₅ was fed1,000 times at intervals of 5 sec, each time lasting 5 sec. However, theflow rate fc of C₂H₅ was treated as a parameter and fc2 was varied from0.5-200 sccm and the change in silicon carbide growth rate was observed(fc1=0, that is, pc1=0).

[0115] Table 2 shows the changes in growth rates of silicon carbide byfc2. When fc2/fs (that is, pc2/ps) was Ss/Sc (0.68) or greater, thegrowth rate of silicon carbide exceeded 10 μm/hr and the effect of thepresent invention was marked. However, when fc2/fs (that is, pc2/ps) wasless than Ss/Sc (0.68), not only did the growth rate of silicon carbidedecrease, but silicon precipitated in the silicon carbide, precludingthe effect of the present invention. Further, when fc2/fs (that is,pc2/ps) exceeded 6.8, the level of adsorption of C₂H₅ on the substratesurface increased. Since adsorption of SiCl₄ was blocked, the growthrate of silicon carbide dropped precipitously, precluding the effect ofthe present invention.

[0116] Silicon carbide grown at an fc2/fs (that is, pc2/ps) of not lessthan 0.2 and not greater than 5 did not exhibit surface defects such asanti phase boundaries and twin crystals.

[0117] As set forth above, the use of the method of manufacturingsilicon carbide provided by the present invention yields a siliconcarbide growth rate of 10 μm/hr or greater and improves quality. TABLE 2silicon carbide growth rate fc2 (sccm) fc2/fs (pc2/ps) (μm/hr) 0.5 0.025silicon precipitation 1 0.05 silicon precipitation 1.5 0.075 siliconprecipitation 1.7 0.085 silicon precipitation 2 0.1 1.2 2.3 0.115 1.52.5 0.125 1.5 3 0.15 1.5 4 0.2 2.1 5 0.25 3.8 10 0.5 6.7 15 0.75 22 20 171 25 1.25 67 30 1.5 65 35 1.75 65 40 2 61 50 2.5 61 100 5 52 200 10 0

[0118] Although a cold wall type CVD device was employed in the presentembodiment, the same effects can be achieved in the present embodimentusing a hot wall type CVD device.

[0119] Further, although the silicon {001} plane was employed assubstrate, the same rapid growth and crystal properties as in thepresent embodiment can be achieved using the silicon {111} plane, cubicsilicon carbide {001} plane, cubic silicon carbide {111} plane, cubicsilicon carbide {−1, −1, −1} plane, hexagonal silicon carbide {1,1,−2,0}plane hexagonal silicon carbide {0, 0, 0,l } plane, hexagonal siliconcarbide {0, 0, 0, 4} plane, and hexagonal silicon carbide {1, −10, 0}plane.

[0120] Although C₂H₅ was employed as the carbon source and SiCl₄ as thesilicon source in the present embodiment, so long as the partialpressure ratio (flow rate ratio) of the carbon source to the siliconsource is not less than one time and not more than ten times theattachment coefficient ratio, at least one member selected from thegroup consisting of CH₄, C₃H₈, C₂H₂, C₂H₆, C₂H₄, C₂H₆, CCl₄, CHF₃, andCF₄ can be employed as the carbon source, and at least one memberselected from the group consisting of SiH₄, Si₂H₆, SiH₂Cl₂, SiHCl₃,Si(CH₃)₄, SiH₂(CH₃)₂, SiH(CH₃)₃, and Si₂(CH₃)₆ can be employed as thecarbon source to achieve the effect of the present invention.

[0121] Embodiment 4

[0122] Employing the {001} plane of a single-crystal silicon substrateas the single-crystal growth substrate, the substrate was heated to atemperature of 1,200° C., and cubic silicon carbide was epitaxiallygrown on the upper layer thereof. Using a cold wall type CVD device, thepressure was adjusted through the introduction of Ar to a pressure of100 mTorr during growth. The growth of silicon carbide on the siliconsubstrate was conducted by feeding feedstock gases in the form ofSiH₂Cl₂ and C₂H₂. The ratio Ss/Sc of the attachment coefficients ofSiH₂Cl₂ and C₂H₂ on the surface of the silicon carbide was 0.25.

[0123] The embodiment of the present invention will be described basedon FIG. 8 below. While continuously feeding SiH₂Cl₂, C₂H₂ wasintermittently fed to grow silicon carbide. The C₂H₂ flow rate (fc2) wasa constant 10 sccm (fc1=0, that is, pc1=0). C₂H₂ was intermittently fed1,000 times at intervals of 5 sec for 5 sec each time. However, the flowrate fs of SiH₂Cl₂ was treated as a parameter and fs was varied from 15sccm to 200 sccm and the change in silicon carbide growth rate wasobserved.

[0124] Table 3 shows the changes in growth rates of silicon carbide byfs. When fc2/fs (that is, pc2/ps) was Ss/Sc (0.25) or greater, thegrowth rate of silicon carbide exceeded 10 μm/hr and the effect of thepresent invention was apparent. However, when fc2/fs (that is, pc2/ps)was less than Ss/Sc (0.25), not only did the growth rate of siliconcarbide decrease, but silicon precipitated in the silicon carbide,precluding the effect of the present invention. Further, when fc2/fs(that is, pc2/ps) exceeded 2.5, the level of adsorption of C₂H₂ on thesubstrate surface increased. Since adsorption of SiH₂Cl₂ was blocked,the growth rate of silicon carbide dropped precipitously, precluding theeffect of the present invention.

[0125] Silicon carbide grown at an fc2/fs (that is, pc2/ps) of not lessthan 0.2 and not greater than 10 did not exhibit surface defects such asanti phase boundaries and twin crystals.

[0126] As set forth above, the use of the method of manufacturingsilicon carbide provided by the present invention yields a siliconcarbide growth rate of 10 μm/hr or greater and improves quality. TABLE 3silicon carbide growth rate fc2 (sccm) fc2/fs (pc2/ps) (μm/hr) 0.1 100 00.5 20 0 1 10 5 5 2 13 10 1 24 15 0.67 24 20 0.5 24 25 0.4 23 30 0.33 2135 0.29 17 40 0.25 11 45 0.22 7 50 0.2 7 60 0.17 5 70 0.14 5 80 0.13Silicon precipitation 90 0.11 Silicon precipitation 100 0.1 Siliconprecipitation 150 0.067 Silicon precipitation 200 0.05 Siliconprecipitation

[0127] Although a cold wall type CVD device was employed in the presentembodiment, the same effects can be achieved in the present embodimentusing a hot wall type CVD device.

[0128] Further, although the silicon {001} plane was employed assubstrate, the same rapid growth and crystal properties as in thepresent embodiment can be achieved using the silicon {111} plane, cubicsilicon carbide {001} plane, cubic silicon carbide {111} plane, cubicsilicon carbide {−1, −1, −1} plane, hexagonal silicon carbide {1,1,−2,0}plane, hexagonal silicon carbide {0, 0, 0, 1} plane, hexagonal siliconcarbide {0, 0, 0, −1} plane, and hexagonal silicon carbide {1, −10, 0}plane.

[0129] Although C₂H₂ was employed as the carbon source and SiH₂Cl₂ asthe silicon source in the present embodiment, so long as the partialpressure ratio (flow rate ratio) of the carbon source to the siliconsource is not less than one time and not more than ten times theattachment coefficient ratio, at least one member selected from thegroup consisting of CH₄, C₃H₈, C₂H₅, C₂H₆, C₂H₄, C₂H₆, CCl₄, CHF₃ andCF₄ can be employed as the carbon source, and at least one memberselected from the group consisting of SiH₄, Si₂H₆, SiCl₄, SiHCl₃,Si(CH₃)₄, SiH₂(CH₃)₂, SiH(CH₃)₃, and Si₂(CH₃)₆ can be employed as thecarbon source to achieve the effect of the present invention.

[0130] Embodiment 5

[0131] Employing the {001} plane of a single-crystal silicon substrateas the single-crystal growth substrate, the substrate was heated to atemperature of 1,200° C., and cubic silicon carbide was epitaxiallygrown on the upper layer thereof. Using a cold wall type CVD device, thepressure was adjusted through the introduction of Ar to a pressure of100 mTorr during growth. The growth of silicon carbide on the siliconsubstrate was conducted by feeding feedstock gases in the form ofSiH₂Cl₂ and C₂H₂. The ratio Ss/Sc of the attachment coefficients ofSiH₂Cl₂ and C₂H₂ on the surface of the silicon carbide was 0.25.

[0132] The embodiment of the present invention will be described basedon FIG. 9 below. While continuously feeding SiH₂Cl₂, C₂H₂ wasintermittently fed to grow silicon carbide. The SiH₂Cl₂ flow rate was aconstant 10 sccm, and the C₂H₂ flow rate (fc2) was a constant 10 sccm(fc1=0, that is pc1=0). C₂H₂ was repeatedly fed 1,000 times at interalsof 5 sec. However, the time during which C₂H₂ was fed each time, denotedas tc, was taken as a parameter and varied from 0 sec to 60 sec, and thechange in silicon carbide growth rate was observed.

[0133] Table 4 shows the changes in growth rates of silicon carbidebased on tc. When tc was less than 0.1 sec, although the growth rate ofsilicon carbide exceeded 10 μm/hr, the reaction between C₂H₂ and SiH₂Cl₂was promoted in the vapor phase. Since the formation of silicon carbidewas impeded at semicrystal positions, single crystal silicon carbide wasnot obtained. When tc exceeded 30 sec, the growth time of siliconcarbide lengthened and the adsorption of C₂H₂ on the substrate surfaceinhibited the adsorption of SiH₂Cl₂, causing the growth rate of siliconcarbide to drop below 10 μm/hr. Accordingly, the effect of the presentinvention appears at a tc of not less than 0.1 sec and not greater than30 sec.

[0134] Silicon carbide grown at a tc of not less than 0.1 sec and notmore than 45 sec did not exhibit surface defects such as anti phaseboundaries and twin crystals.

[0135] As set forth above, the use of the method of manufacturingsilicon carbide provided by the present invention yields a siliconcarbide growth rate of 10 μm/hr or greater and improves quality. TABLE 4Growth rate of silicon tc (sec) carbide (μm/hr) Crystal properties 0 87formation of silicon layer 0.05 85 polycrystal 0.1 70 single crystal 0.569 single crystal 1 62 single crystal 3 64 single crystal 5 61 singlecrystal 8 58 single crystal 10 61 single crystal 15 40 single crystal 2035 single crystal 25 21 single crystal 30 11 single crystal 35 7 singlecrystal 40 7 single crystal 45 5 single crystal 50 0 60 0

[0136] Although a cold wall type CVD device was employed in the presentembodiment, the same effects can be achieved in the present embodimentusing a hot wall type CVD device.

[0137] Further, although the silicon {001} plane was employed assubstrate, the same rapid growth and crystal properties as in thepresent embodiment can be achieved using the silicon {111} plane, cubicsilicon carbide {001} plane, cubic silicon carbide {111} plane, cubicsilicon carbide {−1, −1, −1} plane, hexagonal silicon carbide {1, 1, −2,0} plane, hexagonal silicon carbide {0, 0, 0, 1} plane, hexagonalsilicon carbide {0,0,0,−1} plane, and hexagonal silicon carbide {1, −10,0} plane.

[0138] Although C₂H₂ was employed as the carbon source and SiH₂Cl₂ asthe silicon source of the present embodiment, so long as the partialpressure ratio (flow rate ratio) of the carbon source to the siliconsource is not less than one time and not more than ten times theattachment coefficient ratio, at least one member selected from thegroup consisting of CH₄, C₃H₈, C₂H₅, C₂H₆, C₂H₄, C₂H₆, CCl₄, CHF₃, andCF₄ can be employed as the carbon source, and at least one memberselected from the group consisting of SiH₄, Si₂H₆, SiCl₄, SiHCl₃,Si(CH₃)₄, SiH₂(CH₃)₂, SiH(CH₃)₃, and Si₂(CH₃)₆ can be employed as thecarbon source to achieve the effect of the present invention.

[0139] Embodiment 6

[0140] Seed crystals were prepared from the silicon carbides obtained inEmbodiments 1-5 and silicon carbide was grown by vapor growth epitaxy onthe surfaces of these seed crystals.

[0141] While heating a seed crystal in the form of an SiC substratebased on the present invention to 1,200° C. under vacuum, 1 sccm ofsilane gas and 0.5 sccm of propane gas were introduced, and 1 slm of adelution gas in the form of Ar was supplied. While maintaining thepressure in the reaction system at 100 mTorr, SiC was grown anew on theSiC seed crystal substrate. The seed crystal comprised cubic siliconcarbide grown on a Si (001) substrate, and the silicon carbide that grewon the seed crystal was also cubic silicon carbide. The planar defectdensity of the seed crystal was 700/cm², while that of the newly grownsurface decreased to 30/cm². Thus, it was possible to obtain extremelyhigh quality silicon carbide of large (6 inch) bore.

[0142] In addition to the above-described vapor phase epitaxy, othermethods such as sublimation recrystallization and liquid deposition canbe employed to form silicon carbide on seed crystal.

[0143] Embodiment 7

[0144] The silicon carbide obtained in Embodiments 1-5 can be employedas seed crystal, upon which diamond, gallium nitride (GaN), or diamondand gallium nitride may be formed to obtain composite materialscomprised of silicon carbide and diamond, composite materials comprisedof silicon carbide and gallium nitride, and composite materialscomprised of silicon carbide, diamond, and gallium nitride.

[0145] A seed crystal of cubic silicon carbide grown on an Si (001)substrate and prepared based on the present invention was placed in avacuum chamber and heated to 500° C. Propane gas was then introducedinto the vacuum chamber and the gas evacuation system was adjusted togenerate a pressure within the chamber of 10 mTorr. Next, a 13.56 MHzhigh-frequency (200 W) was applied between the seed crystal and a flatelectrode facing the seed crystal to form a plasma. Carbon decomposingdue to the plasma was deposited on the seed crystal and kept in theproper crystal position, forming diamond on the seed crystal. Thecrystal orientation of the diamond surface was the (001) plane, as wasthat of the seed crystal, and the planar defect density decreased to120/cm². Thus, it was possible to obtain extremely high quality diamondwith a large (6 inch) bore.

[0146] Gallium nitride was also formed on a seed crystal in thefollowing manner.

[0147] A substrate (seed crystal) of silicon carbide obtained by themanufacturing method of the present invention was placed in a vacuumchamber and heated to 1,040° C. Next, 10 slm of ammonia and 0.5 sccm oftrimethylgallium were introduced into the reaction vessel, and while thegases decomposed over the seed crystal, GaN formed at the proper crystalposition. The GaN that formed was, like the seed crystal, a cubiccrystal the surface of which was the (001) plane. The planar defectdensity was 700/cm², identical to the seed crystal. Thus, it waspossible to obtain extremely high quality GaN of large (6 inch) bore.

[0148] Since the crystal defects of silicon carbide employed as seedcrystal are suppressed and various materials can be grown and formed onsuch seed crystals, it is possible to obtain high-quality siliconcarbide materials and composite materials.

[0149] Further, gold and nickel electrodes were formed by the usualmethods on a composite material consisting of diamond formed on theabove-described silicon carbide to prepare Schottky barrier diodes.

[0150] Blue light emitting diodes were obtained using a compositematerial consisting of gallium nitride formed on the above-describedsilicon carbide.

[0151] Since a composite material formed using seed crystal in the formof silicon carbide with no crystal defects is employed in the Schottkybarrier diodes and blue light emitting diodes, good characteristics canbe achieved in semiconductor elements.

[0152] Thus, based on the present invention, it is possible tomanufacture high-quality silicon carbide affording good ease ofproduction since the rate of growth of silicon carbide can be increasedwithout a corresponding increase in crystal defects.

[0153] Further, based on the present invention, silicon carbide andcomposite materials can be obtained in which crystal defects aresuppressed.

What is claimed is:
 1. A method of manufacturing silicon carbide byforming silicon carbide on a substrate surface from an atmospherecontaining a silicon carbide feedstock gas, characterized in that: saidsilicon carbide feedstock gas comprises at least a silicon source gasand a carbon source gas; the partial pressure ps of said silicon sourcegas in said atmosphere is constant (with ps>0), the partial pressure ofsaid carbon source gas in said atmosphere consists of a state pc1 and astate pc2 (where pc1 and pc2 denote partial pressures of said carbonsource gas, pc1>pc2, and the partial pressure ratio (pc1/ps) fallswithin a range of 1-10 times the attachment coefficient ratio (Ss/Sc),the partial pressure ratio (pc2/ps) falls within a range of less thanone time the attachment coefficient ratio (Ss/Sc) (where Ss denotes theattachment coefficient of silicon source gas to the silicon carbidesubstrate at the substrate temperature during formation of said siliconcarbide, and Sc denotes the attachment coefficient of carbon source gasto the silicon carbide substrate at the substrate temperature during theforming of said silicon carbide)) that are repeated in alternatingfashion (referred to as condition 1 below); or the partial pressure pcof said carbon source gas in said atmosphere is constant (with pc>0),the partial pressure of said silicon source gas in said atmosphereconsists of a state ps1 and a state ps2 (where ps1 and ps2 denotepartial pressures of said silicon source gas, ps1<ps2, and the partialpressure ratio (pc/ps1) falls within a range of 1-10 times theattachment coefficient ratio (Ss/Sc), the partial pressure ratio(pc/ps2) falls within a range of less than one time the attachmentcoefficient ratio (Ss/Sc) (where Ss denotes the attachment coefficientof silicon source gas to the silicon carbide substrate at the substratetemperature during formation of said silicon carbide, and Sc denotes theattachment coefficient of carbon source gas to the silicon carbidesubstrate at the substrate temperature during the forming of saidsilicon carbide)) that are repeated in alternating fashion (referred toas condition 2 below).
 2. The manufacturing method of claim 1 wherein incondition 1, pc1 and pc2 each continue for a prescribed period, and incondition 2, ps1 and ps2 each continue for a prescribed period.
 3. Themanufacturing method of claim 1 wherein silicon carbide is formed on asubstrate the temperature of which is not less than 900° C.
 4. Themanufacturing method of claim 1 wherein said silicon source gas is atleast one member selected from the group consisting of SiH₄, Si₂H₆,SiCl₄, SiHCl₃, SiH₂Cl₂, Si(CH₃)₄, SiH₂(CH₃)₂, SiH(CH₃)₃, and Si₂(CH₃)₆,and said carbon source gas is at least one member selected from thegroup consisting of CH₄, C₃H₈, C₂H₅, C₂H₆, C₂H₂, C₂H₄, CCl₄, CHF₃, andCF₄.
 5. The manufacturing method of claim 1 wherein pc2 or ps1 isessentially
 0. 6. The manufacturing method of claim 1 wherein pc2 isessentially 0, the time during which the partial pressure of the carbonsource gas is set to pc1 is 0.1-30 seconds, and the time during whichthe partial pressure of the carbon source gas is set to pc2 is 0.1-30seconds.
 7. A method of manufacturing silicon carbide wherein siliconcarbide manufactured in claim 1 is employed as seed crystal and siliconcarbide is formed on said seed crystal by vapor phase epitaxy,sublimation recrystallization, or liquid deposition.
 8. Themanufacturing method of claim 7 wherein silicon carbide blocks 4-6inches in bore are formed by vapor phase epitaxy, sublimationrecrystallization, or liquid deposition.
 9. A silicon carbide blockhaving a bore of 4-6 inches.
 10. The silicon carbide block of claim 9wherein the planar defect density is not more than 10³/cm².
 11. Asemiconductor element employing as substrate the silicon carbide blockdescribed in claim 9 or
 10. 12. A method of manufacturing compositematerials wherein silicon carbide manufactured by the method of claim 1is employed as seed crystal and diamond and/or gallium nitride is formedon said seed crystal.